In electronic component industries, demand for lighter, thinner, shorter and smaller components is high, and to meet the demand, it becomes essential to reduce the number of components and combine the components.
For example, for coupling different materials, such as a molding material and a metal material, there has been employed a method in which after components are individually formed, an adhesive is applied, and cured with energy of heat, UV or the like, or a method in which grease is applied to an interface between different materials to fill gaps. This allows a certain level of airtightness to be achieved, but an adhesive coating thickness and a region for application of an adhesive are required, causing a bottleneck in thickness reduction and size reduction of electronic components.
In the injection molding method, a molding material is melted by heating for improving fluidity of the molding material, poured in a mold, and cooled/solidified to obtain a three-dimensionally shaped product. Particularly, for preparing a combined component of a molding material and a metal material, the metal material is placed in a mold beforehand, and insert-molded to combine the materials.
However, conventional insert-molded electronic components have a problem that peeling occurs at a coupled portion of the electronic components under an operation environment, and a problem that in the case of electronic components having a hollow structure. Hence, airtightness at an interface between a molding material and a metal material cannot be maintained, and therefore water or moisture enters the inside (hollow structure) of the electronic component to adversely affect operations of the electronic component.
In view of these problems, methods of surface-treating a metal material have been employed as a technique for enhancing airtightness between a molding material and a metal material, and for example, there have been proposed a method in which a surface of a metal to be inserted is treated with a triazine thiol-based surface treatment agent beforehand [Patent Document 1: Japanese Unexamined Patent Publication No. 2006-179229 (published on 6 Jul. 2006)] and a method in which a roughening treatment is performed by chemical etching [Patent Document 2: Japanese Unexamined Patent Publication No. 2001-225352 (published on 21 Aug. 2001)]. [0008] However, in the method described in Patent Document 1, a surface treatment agent may corrode the inside of an electronic component to cause a failure of electrical characteristics of the electronic component.
The method described in Patent Document 2 has a problem that a loss of a metal surface occurs when a dissolution reaction during etching occurs excessively, and in the case of a metal having a protective layer such as a plating film, the metal will be corroded due to detachment of the protective film by the etching, leading to failure of the electrical characteristics of the electronic component.
In addition, both the methods in Patent Documents 1 and 2 have a problem that the process is complicated because preliminary work such as elaborate washing and drying of a metal surface and surface treatment before insert molding are required. Thus, a technique for changing the above-mentioned situation is desired.